U.S. Fish & Wildlife Service

Blackwater

National Wildlife Refuge

Wildlife Drive

Q

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Take a Drive on

the Wild Side!

1. Moist Soil

Vegetation

Blackwater National Wildlife

Refuge welcomes you to tour our

popular Wildlife Drive which can be

accessed by automobile, bicycle or

on foot. Walking and biking on the

drive is permitted; however, visitors

must remain on the paved road.

While on the Refuge, please obey all

signs, and do not feed or harass the

wildlife.

This guide points out some of

Blackwater’s wildlife management

programs. It is keyed to

observation points along the drive.

National Wildlife Refuges provide

protection, food and cover for

wildlife through specific land and

water management programs.

Although the Refuge is managed

primarily for migratory birds and

endangered species, many other

types of wildlife share the wide

diversity of habitats. The careful

observer will see a variety of plants

and animals along the drive.

Freshwater habitat is scarce on

Blackwater Refuge because of the

predominantly brackish (mixture of

salt and fresh water) conditions in

the vicinity. The freshwater

impoundment to your right (you are

riding on the dike) was constructed

to add to the diversity of habitat for

wildlife. The small islands provide

cover and nesting habitat for

waterfowl.

Scan the shallow edges for dabbler

ducks, such as mallards and

Northern pintails; wading birds

such as great blue herons and great
egrets; and shorebirds like

yellowlegs and dunlins. In the

summer the impoundments are

drained to encourage the germination

of natural moist soil vegetation, such

as wild millet, smartweed, and

redroot cyperus which provide food

for waterfowl. The drained mudflats

also provide good feeding areas for

shorebirds and other marsh and

water birds.

In the late summer, the water control

structures are closed to allow rainfall

to fill them, making the seeds and

tubers of these plants and a variety of

invertebrates, such as snails, worms,

and larvae, available to the migratory

waterfowl.

The water to your left is part of the

Little Blackwater River. The river is

named Blackwater because of the

dark color from tannic acids picked

up as it drains through peat soil in the

marshes.

At this point, if you would like to visit

the Observation Point and the Marsh

Edge Trail, you may take the road to

the left. To then rejoin the wildlife

drive, double back and continue from

here. A self-guiding leaflet for

interpreting the Marsh Edge Trail is

available at the trail head.

On your left is a bluebird nest box.

These boxes have been erected to

help improve bluebird reproduction.

Bluebird nesting sites have decreased

due to the lack of natural nesting

cavities. Nesting boxes are being

installed in suitable habitat to allow

the species to nest. Other birds such

as tree swallows, chickadees, titmice,

and wrens may also use the boxes.

Bluebirds, as well as the other

species, consume large quantities of

insects, especially mosquitoes. As

many as 140 bluebirds have been

fledged in one year from the Refuge’s

boxes.

2. Bluebird Box
3. Wood Duck

Box

4. Prothonotary

Warbler Box

5. Delmarva

Fox Squirrel

A few duck species use hollow trees

for nesting. Blackwater, the only

cavity nesting duck is the wood duck.

Timbering and land clearing for

agriculture and development have

eliminated many of the mature

forests which historically provided

an abundance of trees with natural

cavities. These nesting boxes are

used effectively to replace

disappearing natural sites. When

not occupied by wood ducks, the

boxes may have flickers,

sparrowhawks, and screech owls as

tenants. The Refuge maintains

about 200 wood duck boxes

which fledge an average of

600 wood ducks a year.

Notice the cone shape

structures below the boxes. This is

called a “predator guard”, which

helps keep out nest predators such

as raccoons and snakes.

Prothonotary warblers are one of the

two cavity nesting warblers in the

United States. Most warblers build

their nests in small trees or shrubs,

or on the ground. Prothonotary

warblers prefer natural cavities

(decaying snags) located over water

in swampy lowland forest or river

bottom woodlands. Humans have

reduced and altered natural habitats

making nesting sites increasingly

more difficult to find. Since these

warblers do not excavate their own

holes so they compete with other

cavity nesters like Downy

woodpeckers, Carolina chickadees,

and Carolina wrens for nest sites.

This woodland is managed to provide

habitat for the endangered

Delmarva fox squirrel which prefers

a mature forest with little

undergrowth. At one time these

large squirrels, extended from

southeastern Pennsylvania to

Virginia, but natural populations are

now found in only four counties on

Maryland’s Eastern Shore. They
have become endangered, in part,

due to the conversion of forests to

agriculture and development for

human use. Blackwater Refuge

provides habitat and protection to

the largest remaining natural

population of Delmarva fox squirrels

in the world. The Delmarva fox

squirrel has a light, steel-gray coat

and a large fluffy silvery tail with

black edges. The gray squirrel,

which also inhabits the Refuge, is

smaller and has reddish or brown

hair mixed in with the gray coat.

The Delmarva fox squirrel feeds

more on the ground than the gray

squirrel and can be seen venturing

further into fields to feed on

agricultural products.

You will pass a parking area on your

right for one of the Refuge’s walking

trails, the Woods Trail. In Spring,

these wet woods are alive with the

calls of mating tree frogs and toads

and numerous songbirds. The

Woods Trail allows you to trek

through Delmarva fox squirrel

habitat and hopefully observe this

endangered species. If you choose

to hike the one-half mile woodland

trail, you may want to apply insect

repellant, as biting insects are

abundant from mid-April through

late September.

An important part of wildlife

management at Blackwater is the

diversity of the agricultural fields.

More than 800 acres of croplands

are planted with millet, sorghum

(milo), corn, buckwheat, clover,

6. Deer
Key Wallace

Visitor

Center

335

Visitor Center

Auto Drive and

Bike Trail (5 mi.)

Walking Trail

Parking Area

Wildlife Drive Stops

Eagle Resting Sites

Wooded Area

Marsh

Observation Site

Legend

To Cambridge 0 .5

0

soybeans, or rye grass to provide

high energy food and cover for many

species of wintering waterfowl and

other wildlife. White-tailed deer may

be seen feeding in these fields,

especially in the early morning or

evening. They prefer the “edge”

habitat where forests, meadows, and

croplands come together. In addition

to white-tailed deer, smaller, whiterumped sika (pronounced “see-kuh”)

deer, which is an Asian species of elk

introduced to James Island in 1916,

can also been observed at

Blackwater. Abundant in the marshy

areas, sika deer are grazers that

feed on the marsh grasses, while the

white-tailed deer are primarily

browsers that feed on the leaves,

buds and twigs in forested areas.

Both species, however, use

agricultural crops.

 As you drive through the Refuge,

you may notice that some of the

Canada geese are wearing numbered

neck collars. The collars (white on

migratory geese, yellow on resident

geese) were placed on the geese to

obtain information on their movements and abundance in different

areas. Many of the waterfowl also

wear numbered aluminum leg bands.

The waterfowl are captured in nets

or wire traps, identified, banded

and then released. Each bird’s

species, age, sex, and date and

place of banding are recorded

by the Refuge staff and forwarded

to the Banding Laboratory in Laurel,

Maryland. Recovered bands are

turned in by hunters, or band

numbers are reported by other

banding stations when these birds

are recaptured. Information on

migration and other aspects of their

life history are valuable for proper

waterfowl management. Species of

waterfowl using Blackwater include

Canada and snow geese, tundra

(whistling) swans, and more than 20

species of ducks.

7. Waterfowl
From here you can see typical

habitat used by waterfowl, marsh

birds, and muskrats. The dike you

are on separates the

freshwater

impoundments

on your right

from the tidal,

brackish marsh and

Blackwater River on

your left. The

impoundments are

drained in the summer to

allow growth of moist

soil plants, and in some

impoundments, the

planting of crops such as

japanese millet or milo. The

impoundments are then flooded in

the fall mainly through rainfall.

By carefully controlling water levels

in the impoundments, abundant

high energy and protein foods, and

resting sites are made readily

available to the waterfowl and other

migratory birds that depend on the

Refuge from fall to spring.

In late winter prescribed burning

is undertaken in the marsh to

remove dead vegetation. This helps

to promote new, vigorous spring

growth of the Olney three-square

(Scirpus americanus) and other

marsh vegetation that is eaten by

waterfowl, muskrats, and nutria.

Burning also prevents the buildup

of the dried vegetation that can

cause extremely hazardous and

volatile conditions that can fuel

wildfires.

During the summer, egrets, herons,

and other water birds feed on fish

and crustaceans of the brackish

marsh. They also eat frogs and

snakes found in the fresh waters

of the impoundments. Turtles are

often seen sunning themselves on

the logs. Approximately 45 species

of reptiles and amphibians are found

on the Refuge.

8. Fresh and

Brackish Water

Marshes
Muskrats, sometimes observed

swimming in the water, not only feed

on the marsh vegetation, but also

use it to build dome shaped homes

called lodges. These can be readily

seen after prescribed burning of

the marsh, but are hard to find

in the summer when the marsh

vegetation grows higher than

 the lodges. The large rodents

reproduce very rapidly. The young

are considered adults in approximately two months. Trapping by

permit is used to control the

muskrat population, and prevent

damage to the marsh vegetation

from overgrazing.

The nutria, a much larger South

American rodent, was introduced in

this area in the 1940’s for their fur.

Nutria burrow into the marsh to

feed on the roots of marsh plants.

They reproduce more rapidly than

the muskrat, do not have any

natural predators, and there is little

demand for their fur. As a result,

the population is expanding and

causing a great deal of damage to

the marsh. Large mud flats where

nutria have destroyed the marsh

vegetation are visible at low tide.

The nesting platform to your left

helps to compensate for the scarcity

of suitable tall trees near the water

on which osprey would normally

build their nests. The shallow water

surrounding the structure provides

excellent fishing habitat for this

“fish hawk.”

The osprey, is staging a comeback

after its decline as a result of

pesticide use and increased human

activity. The pesticide, DDT, which

caused the eggs that were laid by

these birds to be too thin and too

soft to hatch, was banned in the

United States in 1972. This

legislation and various management

techniques has helped raise the

9. Muskrat and

Nutria

10. Osprey
population of the osprey as well as

other raptors such as the bald eagle

and the peregrine falcon.

The dead tree “snags” to your left

are a favorite resting spot for the

threatened bald eagle as well as for

hawks, vultures, herons, and egrets.

Bald eagles prefer the tall loblolly

pines isolated near the water for

nesting and roosting. Areas on

Blackwater Refuge where eagles

nest are protected from human

disturbance to prevent nest

abandonment. There are

approximately 60 eagles on the

Refuge year round, with winter

populations often exceeding 150.

Another endangered species, the

peregrine falcon, migrates through

the Refuge in the fall and spring.

Blackwater is one of more than 510

refuges in the National Wildlife

Refuge System administered by the

U.S. Fish and Wildlife Service. The

National Wildlife Refuge System is a

network of lands and waters

managed specifically for the

protection of wildlife and wildlife

habitat and represents the most

comprehensive wildlife management

program in the world. Units of the

system stretch across the United

States from northern Alaska to the

Florida Keys and include small

islands in the Caribbean and South

Pacific. The character of refuges is

as diverse as the nation itself. The

Service also manages National Fish

Hatcheries, and provides Federal

leadership in habitat protection, fish

and wildlife research, technical

assistance and the conservation and

protection of migratory birds,

certain marine mammals, and

threatened and endangered species.

Illustrations © Alex Briggs

11. Bald Eagle

U.S. Fish and

Wildlife

Service
Blackwater National Wildlife Refuge

2145 Key Wallace Drive

Cambridge, Maryland 21613-9535

410/228 2677

fax 410 228 3261

email RSRW_BWNWR@mail.fws.gov

Hearing impaired visitors may call the

Maryland Relay Service at TDD/800 735 2258 voice

U.S. Fish & Wildlife Service

1 800/344 WILD

http://www.fws.gov

January 1999